1. Field
Embodiments of the present invention relate to a pen-type optical mouse, and more particularly to a trajectory-estimation apparatus and method that can estimate the trajectory of a pen-type optical mouse in a pen-up state.
2. Description of the Related Art
A conventional pen-type character-input system is provided with a microcode entered in advance, indicating coordinates for a paper used for character input, and estimates the trajectory of a pen through optical-position-recognition technology. Another conventional pen-type character-input system performs a character input by recognizing coordinates according to a movement of an electronic pen while a user takes notes on a tablet or an electronic pen that can recognize coordinates using the electronic pen, and restoring the trajectory of the electronic pen. Such systems based on absolute coordinates perform the pen-trajectory restoration relatively well, but require installation of an additional reference system (i.e., tablet or electronic pen) for providing the absolute coordinates.
In order to overcome such a problem, attempts have been made to create a character-input system based on relative coordinates, instead of the absolute coordinates, using an inertial sensor. As an example, a system for restoring the trajectory by calculating the movement of a pen tip using an inertial sensor only has been proposed. Under this system, however, the accumulated error of the inertial sensor becomes greater over time, and thus an apparatus for compensating the accumulated error is additionally required. As another example, a system for calculating relative coordinates using a ball mouse in a pen-down state and estimating the trajectory of a pen-type mouse using an inertial sensor in a pen-up state has been proposed. However, this system requires two kinds of sensor modes for pen-up and pen-down states.